The invention relates to a spring-loaded hinge for furniture doors with two hinge guide rods, pivotably hinged, on the one hand, at a door stop part and, on the other, at a supporting wall stop part, which is constructed as an extended supporting arm, in the form of a quadruple joint. In the course of swiveling from the closed position into the open position, the quadruple joint can be moved over a dead center position, on this side of which it is pushed by the tension of a leg spring into the closed position and on the other side of which it is pushed by the tension of the leg spring into the opening direction, one leg of the leg spring, disposed in the door-side end region of the supporting arm, engaging an extension of the outer hinge guide rod, which is remote from the supporting wall, forming a lever arm with the swiveling axis of this guide rod on the side of the supporting arm and the other leg of the leg spring being supported at the hinge pin of the inner hinge guide rod on the side of the supporting arm.
In the case of known spring-loaded hinges with leg spring (DE 27 03 498 C2), the leg spring is held in the intended position in the interior of the supporting arm by a pin, which passes through the leg spring and is riveted in the lateral side walls of the supporting arm. Since they carry out swiveling motions during the opening and closing movement of the hinge from the extension of the outer hinge guide rod on the one hand and from the end of the leg of the leg spring engaging it, about center points of radii, which are at a distance from one another, the point of attack of the leg at the extension is shifted during the movement of the hinge, as a result of which the lever arm, under which the pre-tension of the leg acts on extension, changes and the region of attack of the leg at the extension is shifted. As a result of the pre-tension of the leg, a not negligible friction occurs between the extension and the leg and, under unfavorable circumstances, can lead to frictional wear in the surfaces sliding on one another. In addition, the portion of the pre-tension of the spring, required to overcome the frictional forces, is unavailable for producing the opening and closing moments of the spring-loaded mechanism. The pre-tension of the leg springs must be increased correspondingly to take into consideration the frictional forces that occur. This, in turn, results in increased frictional wear and requires a corresponding dimensioning of the leg spring.
It is an object of the invention to develop the known hinge so that, during the opening and closing movement of the hinge, translatory sliding movements of the stop region of the leg of the leg spring do not occur at the extension of the outer hinge guide rod.
Starting out from a spring-loaded hinge of the type named above, this objective is accomplished pursuant to the invention owing to the fact that the leg spring is constructed as a double leg spring with a middle double leg of two parallel leg arms, protruding between two groups of spring coils from, in each case, one inner spring coil, and two outer legs, protruding from the in each case outermost spring coil, that the middle double leg is constructed arc-shaped at its free end and embraces the hinge pin, which carries the hinge guide rod pivotably, at least partially with this arc-shaped end through a central recess in the bearing lug of the inner hinge guide rod on the side of the supporting arm and is held rotatably on the hinge pin, that the free ends of the leg, protruding from the outer spring coils, are held in a recess of the extension of the outer hinge guide rod so that they can be rotated about an axis extending parallel to the axis of the bearing pin of the outer hinge guide rod on the side of the supporting arm, and that the double leg spring is held exclusively by the double leg and the outer leg in the supporting arm. The leg spring, which is now constructed as a double leg spring, is thus held exclusively, in the case of the inventive spring-loaded mechanism, by the rotatable mounting of the ends of the double leg at a hinge pin on the one hand and the outer leg is held in the recesses of the extension of the outer hinge guide rod in the interior of the supporting arm, so that the part of the double leg spring, formed by the spring coils, is able to change its position in the interior of the supporting arm without resistance. There is therefore no translatory displacement movement of the ends of the legs engaging the extension of the outer hinge guide rod during the opening and closing movements of the hinge. On the other hand, during the relatively slight rotational movement of the outer ends of the hinge guide rod in the extension, only negligibly little friction develops, so that frictional wear is practically precluded and, essentially, the whole pretension is available for producing the opening or closing moment of the spring-loaded mechanism.
If the outer hinge guide rod is mounted on the side of the supporting arm owing to the fact that it has at its opposite longitudinal edges bent side walls, in which the supporting boreholes for the hinge pin on the side of the supporting arm are provided, the configuration takes place in an inventive, further development so that the extension is formed in each case by an elongation of the side walls, and that in each of the two elongations an open recess is provided, in which in each case an end section of the respective leg of the double leg spring, bent into a position parallel to the axis of the hinge pin, located on the side of the supporting arm, of the outer hinge guide rod, engages rotatably relative to the respective elongation. In contrast to the length of the bent end section of the leg, engaging the underside of the continuation of the outer hinge guide rod of the (single) leg spring of the known hinges, extending essentially over the whole width of the extension, the bent end sections can be kept so short pursuant to the invention that there still is free space between them.